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Unable to authenticate and send email using a 3rd party app on a Mediacom provided IP address

I have a home IP address in the 173.23.46.x subnet.  Since November 10, I cannot use any 3rd party email app on two android phones or my desktop computer when connected to the Mediacom provided IP address.  Previous to November 10 all 3rd party email apps worked okay for years. Now I keep getting an error of " Cannot verify account.  Server does not support authentication. "  However if I turn off WiFi on our phones and use Verizon cell data access, the 3rd party apps work and can authenticate, so my credentials are good.  If I use WiFI with a NordVPN connection, the 3rd party email apps work okay on my computer (hardwired not on WiFi) and cell phones in the house.
I noticed that every Mediacom address within the IP range of to is blocked on the list.  According to having an IP address included in this Policy Blocklist (PBL) is standard for the vast majority of internet users and is not the result of my actions.  This listing is controlled by the Internet Service Provider, not Spamhaus.  Thus Mediacom put these IP addresses on the PBL.  Supposedly as a best practice so that users are forced to authenticate to an email  and cannot send email directly to the internet.
I am using the usual email server parameters which Mediacom publishes -
IMAP Server Settings - Authentication Required:
Type:         Server:       Encryption:         Port:
Incoming     SSL    993
Outgoing       STARTTLS     587
If STARTTLS is Not Available:
Type:     Server:       Encryption:         Port: 
 Outgoing       SSL     465
Repeated conversations with Mediacom Total Care have gone nowhere.  They just say they do not troubleshoot 3rd party apps and will not help me or investigate my problem.  They just say to use the web app to read/send email.
I cannot believe everyone else using a Mediacom IP address in this to range is also not able to send using a 3rd party email app.  So what am I doing wrong?
I have a friend in Minnesota using Mediacom, but has an IP address not in this range and he is not having problems with his 3rd party email app.


My apologies, I have not ran into this issue and not too familiar with Spamhaus.

Is there a Spamhaus form that you could fill out for inquiry? I would think if something is blocked, it might be due to an e-mail account sending out spam.

All I could locate is -

I have sent block removal messages to with no response yet .  Sent multiple messages over the last couple of weeks.  Also tried to contact, but they say that being on the PBL is not something I can remove myself from.


If the problem is only occurring on your home connection, I suggest testing with a different modem. 

Not sure how a cable modem would influence a remote mail server to not authenticate.  I can ping the mail server and access it. I will see if I can find someone in town on Mediacom to try out my phone app there.